A conventional liquid crystal display device comprises: a liquid crystal cell, an upper polarizer provided above the liquid crystal cell, a lower polarizer provided below the liquid crystal cell, and a backlight source provided on a side of the lower polarizer away from the liquid crystal cell, where polarization axis directions of the upper polarizer and the lower polarizer are perpendicular to each other. A display principle of the above-described liquid crystal display device is that: different data voltages are applied to respective sub-pixels of the liquid crystal cell respectively, to drive liquid crystal molecules of the respective sub-pixels to be deflected in different degrees; after lights emitted from the backlight source pass through the lower polarizer, they change from natural lights to linearly polarized lights, which then pass through the liquid crystal cell. Since the liquid crystal molecules of the respective sub-pixels of the liquid crystal cell are deflected in different degrees, the linearly polarized lights pass through the respective sub-pixels of the liquid crystal cell and then have their polarization directions to be changed in different manners. Finally, lights pass through the upper polarizer, and the upper polarizer performs polarization analysis on the lights, so that amounts of lights emitted from the respective sub-pixels are different, so as to implement gray-scale display. Since a polarizer only allows a light component whose polarization direction is parallel to a polarization axis direction of the polarizer to pass, there is more light loss when lights pass through the upper polarizer and the lower polarizer, resulting in reduction of light utilization efficiency of the liquid crystal display device.